Check the
appropriate box to designate the rule pursuant to which this Schedule is filed:

¨ Rule
13d-1(b)

x Rule 13d-1(c)

¨ Rule 13d-1(d)

(Continued on following pages)

Page 1 of 6 Pages

[1]

The remainder of this cover page shall be filled out for a reporting persons initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information
which would alter disclosures provided in a prior cover page.

The information required on the remainder of this cover page
shall not be deemed to be filed for the purpose of Section 18 of the Securities Exchange Act of 1934 (Act) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the
Act (however, see the Notes).

Class A Common Shares of Beneficial Interest, Par Value $0.01 Per Share (Shares)

Item 2(e). CUSIP Number: 81752R100

Item 3.

If this statement is filed pursuant to Sections 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:

(a)

[ ]

Broker or Dealer registered under Section 15 of the Act.

(b)

[ ]

Bank as defined in Section 3(a)(6) of the Act.

(c)

[ ]

Insurance Company as defined in Section 3(a)(19) of the Act.

(d)

[ ]

Investment Company registered under Section 8 of the Investment Company Act of 1940.

(e)

[ ]

An investment advisor registered in accordance with Section 240.13d-1(b)(1)(ii)(E);

(f)

[ ]

An employee benefit plan or endowment fund in accordance with Section 240.13d-1(b)(1)(ii)(F);

Page 3 of 6 Pages

(g)

[ ]

A parent holding company or control person in accordance with Section 240.13d-1(b)(ii)(G);

(h)

[ ]

A savings association as defined in Section 3(b) of the Federal Deposit Insurance Act;

(i)

[ ]

A church plan that is excluded from the definition of an investment company under Section 3(c)(14) of the Investment Company Act;

(j)

[ ]

A non-U.S. institution in accordance with Section 240.13d-1(b)(1)(ii)(J);

(k)

[ ]

Group in accordance with Section 240.13d-1(b)(1)(ii)(K).

Item 4.

Ownership

(a)

Amount Beneficially Owned:

As of the date hereof, Warren E. Buffett is the beneficial owner of
2,000,000 Shares.

(b)

Percent of Class:

As of the date hereof, Warren E. Buffett is the beneficial owner of 8.02% of
outstanding Shares (based upon information provided by the Issuer on Form 10-Q filed on November 13, 2015).

(c)

Number of shares as to which such person has:

(i) sole power to vote or to direct the vote:

2,000,000

(ii) shared power to vote or to direct the vote:

0

(iii) sole
power to dispose or direct the disposition of:

2,000,000

(iv) shared power to dispose or to direct the disposition of:

0

Page 4 of 6 Pages

Item 5.

Ownership of Five Percent or Less of a Class.

If this statement is being filed to
report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the securities, check the following [ ]

Not applicable.

Item 6.

Ownership of More than Five Percent on Behalf of Another Person.

Not applicable.

Item 7.

Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.

Not applicable.

Item 8.

Identification and Classification of Members of the Group.

Not applicable.

Item 9.

Notice of Dissolution of Group.

Not applicable.

Item 10.

Certification.

By signing below I certify that, to the best of my knowledge and belief,
the securities referred to above were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a
participant in any transaction having that purpose or effect.

Page 5 of 6 Pages

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true,
complete and correct.